Lubricating or hydraulic process using tertiary alkyl thiophene



United States Patent Olfice 3,395,101 Patented July 30, 1968 ABSTRACT OF THE DISCLOSURE The use as lubricants and hydraulic fluids of compositions selected from the group consisting of: (1) A compound represented by the structure (X) I A'] I A [ha-Lanes] Dm S wherein A, B, C, A, B and D are each selected from the group consisting of branched or straight chain alkyl C groups aryl, haloaryl, alkaryl and aralkyl groups provided at least 2 of A, B and D, and at least 2 of A, B and D' are alkyl C groups; further provided that when alkyl any two of A, B, D and A, B and D groups together with the carbon atom to which they are attached can be members of an alicyclic hydrocarbon ring, X is a halogen, m and n are integers from to 1, providing the sum of m+n is at least 1 and z is an integer from 0 to 2; and

(2) mixtures of (1).

This invention relates to functional fluid compositions and more particularly to lubricants and hydraulic 'fluid compositions comprising certain alkylthiophenes.

As the capability of aircraft powered by gas turbine engines is increased improved lubricants and hydraulic fluids are required because such increased capability usually results in increased operating temperatures of the engines and hydraulic system. Thus, there is now a need for fluids which are thermally stable, resistant to oxidation at elevated temperatures (350450 F.) and yet possess good lubricity, wide liquid range, and are non-corrosive to metals, seals or packing.

Formerly different compositions were used as lubricants than were used as hydraulic fluids to power the various operating mechanisms of an airplane. However, recently it has been found desirable to employ one fluid for both purposes so that improved aircraft could be constructed. Such aircraft contain, for example, hydraulic power system pumps which must be lubricated entirely by the hydraulic fluid. Also, the hydraulic lines and powered units are now exposed to elevated temperatures such that more thermally stable hydraulic fluids are re quired.

Compositions useful as both lubricants and hydraulic fluids have now been discovered which possess thermal and oxidative stability and other desirable properties required for use in aircraft engines and hydraulic systems.

It is, therefore, an object of this invention to provide functional fluid compositions. Another object of this invention is to provide novel compositions having a wide liquid range and high thermal and oxidative stability which are useful both as hydraulic fluids and lubricants.

In accordance with this invention fluids of high thermal and oxidative stability, broad liquid range, low volatility and favorable viscosity for lubricant and hydraulic uses are provided which comprise monoand dialkylthiophenes and mixtures thereof represented by the structure wherein A, B, D, A, B and D are each selected from the group consisting of branched or straight chain alkyl C groups aryl, haloaryl, alkaryl and aralkyl groups provided at least 2 of A, B and D, and at least 2 of A, B and D' are alkyl C groups; further provided that when alkyl any two of A, B, D and of A, B and D groups together with the carbon atom to which they are attached can be members of an alicyclic hydrocarbon ring, X is a halogen, m and n are integers from O to 1, providing the sum of m+n is at least 1 and z is an integer from 0 to 2.

Typical thiophenes of structure I are as follows: 2,5 l-hexyl-1-methylnonyl)thiophene, 3 ,4-( l-hexyll-methylnonyl thiophene, 2,4-( l-hexyl-l-methylnonyl)thiophene, 2,5-tert-butyl-3,4-dichloro thiophene, 2-tert-butyl thiophene, 3-chloro-5-tert-butyl thiophene, 3-tert-butyl thiophene, 3-brom-o-4-( l-hexyl-l -methylnonyl) thiophene, 2,5 -tert-butyl thiophene, 2-tert-butyl-5-( l-hexyll-butyldodecyl thiophene, 2, 5-(1,l-dimethylpropyl)thiophene, 2-fluoro-5-( 1-butyl-l-hexyldodecyl)thiophene, 2,5-( 1-butyl-1-octylnonyl) thiophene, 2-( l-hexyl-l-methylnonyl) -5-( l-butyl-l-propyldecyl) thiophene, 2-tert-butyl-4-( 1-octyl-l-methyloctadecyl) thiophene, 2, 5- l-octyll-methyldecyl thiophene, 3,4- l, l-dimethyloctadecyl thiophene, 2,5 1, l-dimethyltridecyl) thiophene, 2,4-( 1, 1-dioctyloctadecyl) thiophene, 2,4-( 1, l-dimethyltridecyl thiophene, 3,4-( l-octyl-l-nonyloctadecyl) thiophene, 3,4-( 1, l-dimethyltridecyl thiophene, 3-(1,1-dimethyloctadecyl)thiophene, 2- (1,1-dibutylnonyl)thiophene, 3- l-butyl-1-methyloctyl)thiophene, 2-( 1,l-dipentylnonyl)thiophene, 2-(1,l-dihexyloctadecyl)thiophene, 2- l-methylcyclohexyl) thiophene, 2- l-butylcyclopentyl thiophene, 2,5(l-methylcyclooctyl)thiophene, 2,5 l-propylcyclobutyl) thiophene, 2- l-propylcyclobutyl thiophene, 2,5 lphenyl-1-methylnonyl)thiophene, 2- 1 -chlorophenyl- 1 -ethyloctyl thiophene, 2,5 l-methylphenyll-propyldecyl )thiophene, 3-(l-phenyl-1,4-dimethylhexyl)thiophene and 2,5-( l-fluorophenyl-l-methyl-6-propylnonyl) thiophene where R and R are each selected from the group consisting of straight chain alkyl groups aryl, alkaryl, aralkyl, haloaryl groups and R is selected from hydrogen and C branched or straight chain alkyl groups.

The reactionof'thiophene and olefins isaided by known catalysts such as active clays, boron fluoridecom plexes," tin halides," sulfuric acid,"aliiiiiinurrfchloride and hydrogen fluoride. Under catalytic influence the reaction takes place as follows:

III in (Xh H-CH (catalyst) I RC R \R1 \s/ I 1 s/ where R, R X z, and R have the saine meaning as EXAMPLE 1 Into a reactor equipped with a reflux condenser, a liquid addition means and a heating means there were placed 21 parts of thiophene, 100 parts of 2-hexyl-1-decene and 5.6 parts of boron trifluoride ethyl etherate as a catalyst. The reaction mixture was heated slowly to a temperature in the range of from 90 to 100 C. After about 1 hour in that temperature range an additional charge of .23 parts of 2-hexyl-l-decene were added and the mixture was stirred for an additional 3 hours within the same temperature range. The catalyst was then deactivated by the addition of about 11 parts of calcium oxide followed by about 2 hours of continued agitation at 100 C. Solids were separated by filtration and the filtrate was subjected to distillationv at reduced pressure. The distillate, boiling in the range 245-255 (1 mm. Hg) was redistilled to yield a mixture of 2,4- and 2,5- (1'-hexyl-1-methylnonyl)thiophenes which was indicated by g.l.c. to be 99.5% dialkylthiophene content.

EXAMPLE 2 A mixture of monoalkylated thiophenes was prepared by placing into a reaction as described in Example 1, 90 parts of a mixture of aliphatic olefins comprised as follows:

After heating the olefin mixture to about 72 C., 11 parts of boron trifiuoride diethyletherate were added and 22 parts of thiophene were added dropwise over about /2 hour. The reaction mixture was agitated at temperatures in the range of from 75 to C. for an additional 1 /2 hours then 200 parts of water were added. The reaction mixture was cooled and the organic layer separated, washed with 200 parts of 2% sodium hydroxide and filtered through sodium sulfate. The filtrate was vacuum distilled at 243-280 C. (0.8 mm. Hg) yielding 70 parts of a mixture of mono-alkylthiophenes corresponding in composition and proportion to the olefin reactants.

EXAMPLE 3 2 Into a suitable reaction there were placed 95.4 grams (.2 mole) of Z-tridecyl-l-tridecene and 55 parts of boron trifluo ride ethyletherate. Then 168 parts (2 moles) of thiophene were added under a nitrogen blanket at 50 C. The reaction mixture was heated to 80 C. and maintained at the temperature for 9 hours with continuous agitation. Water was added (200 parts) to stop the reaction and the mixture was agitated for an additional 9 hours. The water was then removed, the reaction mixture was washed with 1% sodium hydroxide followed by 2 water washes and then filtered. The filtrate was vacuum distilled to yield 174 parts of 2-(1-tridecyl-1-methyldodecyl)thiophene recovered at a vapor temperature of 218-223.5 C. and at a pressure of 18 mm. of Hg.

Although the alkyl and dialkylthiophenesof this invention are referred to as specific isomers such as the 2- or 2,5-isorners they can contain up to about 30% by.

weight of the corresponding 3- and 2,4 alkyl or dialkyl isomers.

In Table I below there are listed some physical properties of various pure monoand dialkylthiophenes of this invention.

TABLE I.PHYSICAL PROPERTIES OF VARIOUS MONO- AND DIALKYLTHIOPHENES Viscosity (cs. at- Four Compound B.P. C.)/mm. Point 210 F. 100 F. 30,F. 40 F. F.) 1 2,5 (l-hexyI-l-methylnonyl)thiophene 250/0-5 55.5 13,522 29,552 -50 2 2,5-(l-octyl-l-methylundecyl)thiophene.. 295-307/10 71.1 21,000 55,000 +15 3 2,5-(l-l-dimethyltetradecyl)thiophene. 255-257f0 35 4. 2,5-(1,l-dlmethylhexadecyl)thiophene 0/0.! 5. 2,5-(1-dodecylcyclopentyDthiophene. 255.-284/0 2 52.36 50,000 198 6. 2-(1,l-didecyltetradecyl)thiophene 267-269] 4. 52. 99 30,252 40 7. 2-(l-unadecy1-1-methyltetradecyl)thiophene- 250/10... 28. 94 10,000 8 8. 2-(l-uuadecyl-l-methyltridecyDthiophene 237/065.-. 26.23 8, 043 9. 2,5-(1-ethyl-1-methylpentyl)thiophene 163/0.9 13.99 35,868 50 10. 2-(l-hexyl-l-methylnonyl)thiophene 10.61 2,202

* Extrapolated viscosities.

From the above it is evident that the monoand dialkylthiophenes of this invention are especially useful as lubricants and hydraulic fluids throughout a wide temperature range such as is enconutered in aircraft. Lubricants and hydraulic fluids employed in such high temperature applications are required to possess thermal and oxidative stability.

The superior thermal and oxidative stability of the thiophenes of structure I as compared to alkylthiophenes having hydrogen atoms on the alkyl carbon atom bonded to the thiophene nucleus is illustrated by the data in Table II below. In Table II there are presented the results of tests of oxidative stability of fluids wherein samples of the fluid are contacted with oxygen gas for a period of 40 minutes in the presence of metal while the samples are being agitated and maintained at a temperature of 450 F. The amounts of oxygen which pass into and out of the sample are measured and the difference noted as the amount taken up by the fluid. The amount of oxygen taken up by the fluid has been found to be directly proportional to the amount of oxidation occuring in the fluid. Thus, the oxidative stability of various alkylthiophenes were determined and the data presented below as moles of oxygen uptake per mole of fluid contacted by the oxygen gas. A low number is desirable. To determine the oxidative stability of the fluids in the presence of metal, wire specimens of aluminum alloy, magnesium alloy, copper, iron, titanium and silver were placed in the test sample.

TABLE II Mole of 0 uptake Fuild: per mole of fluid 2,5-( l-hexyl-l-methylnonyl)thiophene 0.34 2-(l-undecyl-l-methyltetradecyl)thiophene 1 4 1 Oxygen contact for 360 minutes. 2 Pentaerythritol esterified with a mixture of C t-o aliphatic acids which also contained amine oxidation inhibitors.

The above data illustrates the superior oxidative stability of the compounds of this invention over the n alkyl thiophenes by the comparatively lesser amount of oxygen uptake. Also included in Table II is the results of the test when employing a pentaerythritol ester which was a commercially available formulated gas turbine engine lubricant containing well-known oxidation inhibitors dioctyldiphenylamine and phenyl alpha naphthylamine. The ester was included for the purpose of indicating the inherently superior thermal and oxidative stabilities of the alkylthiophenes of this invention over those of a stabilized functional fluid.

Further evidence of the desirability of the alkyl thiophenes of this invention as lubricants is furnished by the data presented in Table III. These data were obtained from comparative runs in a Shell four ball test machine operated for 1 hour at 600 rpm. under a load of 40 kg. using steel on steel balls. Other fluids tested were commercially available hydraulic fluids. The alkylthiophenes of this invention contained no additive of any kind while the other fluids were formulated with lubricity agents.

TABLE 111 Scar diameter, Lubricant: mm. 2,5-(l-hexyl-l-methylnonyl)thiophene .87 Aliphatic ester lubricant 1.07 Mineral oil .74

The above data indicates the inherent lubricity of the alkylthiophenes of this invention. That is, without additives, the alkylthiophenes of this invention possess lubricity which compares favorably with that of commercially accepted standards achieved by other fluids through the aid of lubricity agents.

In accordance with the above data, it is evident that the monoand dialkylthiophenes of this invention are especially useful as lubricants for gas turbine engines. Thus, this invention relates to a novel method of lubricating gas turbine engines which comprises maintaining on the points of wear of the engine a lubricating amount of a monoor dialkylthiophene of this invention or a mixture thereof.

Preferred compounds of this invention are compounds of Formula I wherein A, B, D, A, B and D are alkyl C groups and the total number of carbon atoms is within the range of from 25 to 35, and mixtures thereof. More preferably that number of carbon atoms is contained in two groups, i.e., where m+n is 2. Typical examples of such preferred compounds are 2,5 (l-hexyl-lmethylnonyl thiophene; 2,4-( l-hexyl-l -methylnonyl thiophene; 2,5-(l-octyl-l-methyl-undecyl)thiophene; 2,5-(1- ethyll-methylpentyl thiophene.

Typical examples of mixtures of mono and dialkylthiophene are 2,5-(l-hexyl-1-methylnonyl)thiophene and 2-( l-undecyl-1-methyltetradecyl)thiophene; 2,5-( l-hexyll-methylnonyl)thiophene and 2-(l-undecyl 1 methyltridecyl)thiophene; 2,5-( l-hexyl-l-methylnonyl)thiophene and 2-(l-hexyl-l-methylnonyl)thiophene; 2,5-(1-octyl-1- methylundecyl)thiophene and 2-(l-undecyl 1 methyltridecyl)thiophene.

As a result of the excellent physical properties of the compound of this invention, improved hydraulic pressure devices can be prepared in accordance with this invention which comprise in combination a fluid chamber and an actuating fluid in said chamber, said fluid comprising a mixture of one or more of the compounds of this invention. In such a hydraulic apparatus wherein a movable member is actuated by the above-described func tional fluids, performance characteristics are obtainable which are superior to those heretofore obtainable.

Because of their low pour points and good lubricity the functional fluids of this invention can be utilized in those hydraulic systems wherein power must be transmitted and the frictional parts of the system lubricated by the hydraulic fluid utilized. Thus, the compounds of this invention find utility in the transmission of power in a hydraulic system having a pump therein supplying the power for the system. In such a system, the parts which are so lubricated include the frictional surfaces of the source of power, namely the pump, valves, operating pistons and cylinders, fluid motors and in some cases for machine tools, the ways, table and slides. The hydraulic system may be of either the constant-volume or the variable-volume type of system.

The pumps may be of various types, including the piston-type pump, more particularly the variable-stroke piston pump, the variable, discharge or variable-displacement piston pump, radial-piston pump, axial-piston pump, in which a pivoted cylinder block is adjusted at various angles with the piston assembly, for example, the Vickers Axial-Piston pump, or in which the mechanism which drives the piston is set at an angle adjustable with the cylinder block; gear-type pump, which may be spur, helical or herringbone gears, variations of internal gears, or a screw pump; or vane pumps. The valves may be stop valves, reversing valves, pivot valves, throttling valves, sequence valves or relief valves. Fluid motors are usually constantor variable-discharge piston pumps caused to rotate by the pressure of the hydraulic fluid of the system with the power supplied by the pump power source. Such a hydraulic motor may be used in connection with a variable-discharge pump to form a variablespeed transmission.

Although the compositions described above are generally quite suitable for most applications, it may also be desirable to add minor amounts, i.e., 5% by weight, of various other functional addition agents such as viscosity index improvers, e.g., a polymerized methacrylate ester, an alkylated polystyrene, or the lpolyether condensation products of ethylene oxide or propylene oxide, or both, with a glycol such as ethylene glycol, propylene glycol, butanediol, etc., or with'an aliphatic alcohol such as butanol, octanol, decanol, tridecanol, etc., pour point depressants, oxidation inhibitors, detergents, corrosionand rust-inhibiting agents, anti-wear and lubricity agents, such as tetraoctyl tin, diphenyl hydrogen phosphite and diisopropyl hydrogen phosphite, anti-foaming agents such as the silicone polymers, and the like.

While this inventionhas been described with respect to various specific examples and embodiments, it is to be understood thatthe invention is not limited thereto and that it be variously practiced within the scope of the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are definedas follows:

'1. The method of lubricating a gas turbine engine which comprises contacting the points of wear of the engine with a lubricating amount of a composition selected from the group conssiting of (1) an alkylthiophene represented by the structure i 151., S Ll) wherein A, B, D, A, B and Dam each selected from the group consisting of branched and straight chain alkyl C groups, aryl, haloaryl, alkaryl and aralkyl groups provided at least 2 of A, B, and D, and at least 2 of A, B and D are alkyl C groups and further provided that when alkyl any two of A, B, D and of A, B and D groups together with the carbon atom to which they are attached can be members of an alicyclic hydrocarbon ring, X is a halogen, m and n are integers from to 1, providing the sum of m-l-n is at least 1 and z is an integer from '0 to 2 and (2) mixtures of (1).

2. The method of claim 1 where m and z are 0.

3. The method of claim 1 where A and A are methyl and z is 0.

4. The method of claim 1 where the alkylthiophene is 2,5 l-hexyl-l-methylnonyl thiophene.

5. The method of claim 1 where the composition is a mixture of dialkylthiophenes.

6. The method of claim 1 where the composition is a mixture of monoand dialkylthiophenes.

7. The method of claim 1 where A, B, D, A, B and D are alkyl C groups and have a total of from 25 to 35 carbon atoms.

8. The method of operating a hydraulic pressure device wherein a displacing force is transmitted to a displaceable member by means of a hydraulic fluid, the improvement which comprises employing as said hydraulic fluid a composition selected from the group consisting of (1) alkylthiophenes represented by the structure wherein A, B, D, A, B and D are each selected from the group consisting of branched and straight chain alkyl C groups, aryl, haloaryl, alkaryl and aralkyl groups provided at least 2 of A, B and D, and at least 2 of A, B and D are alkyl 0 groups and further provided that when alkyl any two of A, B, D and of A, B and D' groups together with the carbon atom to which they are attached can be members of an alicyclic hydrocarbon ring, X is a halogen, m and n are integers from 0 to 1, providing the sum of m+n is at least 1 and z is an integer from 0 to 2 and (2) mixtures of (1).

9. The method of claim 8 where A and A are methyl and z is 0.

10. The method of claim 8 where m. and z are 0.

11. The method of claim 8 where the alkylthiophene is 2,5-( l-hexyl-l-methylnonyl) thiophene.

12. The method of claim 8 where the composition is a mixture of monoand dialkylthiophenes.

13. The method of claim 8 where the composition is a mixture of dialkylthiophenes.

14. The method of claim 8 where A, B, D, A, B and D are alkyl C groups and have a total of from 25 to carbon atoms.

15. The method of claim 1 where the composition contains a minor amount of a viscosity index improver.

16. The method of claim 8 where the composition contains a minor amount of a viscosity index improver.

References Cited UNITED STATES PATENTS 2,528,782 11/1950 Reitf et al. 252- 2,551,644 5/1951 Seger et al 260-329 2,737,536 3/1956 Block et a1. 260-329 X 2,743,280 4/1956 Feasley et al. 260-329 2,932,615 4/1960 Jordan et al. 252-45 X 3,014,056 12/1961 Kerschner et al. 252-56 X 3,069,431 12/ 1962 Krespan 252-78 X 3,096,375 7/ 1963 Campbell et al 252-45 DANIEL E. W'YMAN, Primary Examiner.

W. H. CANNON, Assistant Examiner. 

